Comments

So you have relay mode ON on both your hand-held V6 Tx and the on-camera V6 Rx, correct?

Relay mode must be OFF for all V6 Rx with flashes connected to them.

When a "RELAY TIME OUT" message appears on the on-camera V6 Rx then this means the V6 Rx received the trigger command from your hand-held unit but then did not get a flash trigger command from your camera.

It makes sense that this error message appears in your scenario, as your camera does not take a shot and hence won't create a flash trigger signal for the on-camera V6 Rx.

The question is why the camera is not triggered in your scenario 1. but is triggered in your scenario 2.

What flash are you disconnecting from where to make the triggering of the camera work in scenario 2.?

Can you try to trigger the camera using relay modes for both V6 Tx and V6 Rx by not connecting anything to the camera but the relay V6 Rx via the shutter cable? Don't put the V6 Rx on the camera's hot-shoe yet. Is the camera triggered then?

If so, can you add a flash (in manual mode) to the camera and see whether it is fired by the camera when you remote trigger with the V6 Tx?

If it flashes then all that should be left to do is to replace the on-camera flash with the V6 Rx that is still connected to the camera with the shutter cable. Afterwards, you shouldn't get the time out error message anymore and your remote flashes should be triggered.

BTW, for troubleshooting, it is best to put the camera into manual mode as well to create repeatable conditions. It may not be strictly necessary, but if you could use manual mode for the camera to ensure that it fires an on-camera flash every time, then it would be easier to just add remote triggering to that (and hence be one step away from making your scenario work).